Methods and devices for counteracting hypotension

ABSTRACT

Devices and methods are disclosed to address blood pressure control. More particularly, the present invention relates to correction of transient low blood pressure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/954,933 filed Sep. 3, 2004 which is incorporated in its entiretyherewith.

BACKGROUND OF THE INVENTION

Syncope, commonly known as “passing out,” is a common medical condition.While, seizures and strokes can cause actual loss of consciousness anumber of less severe conditions or factors may also lead to syncope.However, the potential for serious injury as a result of any temporaryloss of consciousness makes syncope a significant medical concern. Forexample, those individual that are otherwise healthy may faceconsiderable injury as a result of the fall from passing out.Alternatively, a minor fall may have serious consequences if theindividual is elderly.

Despite the fact that a number of factors may contribute to syncope, aconsiderable number of these factors are attributable to thecardiovascular system. For example, a slow heart rate, a long pausebetween heartbeats, vessel dilation (know also as vasodilatation),dehydration, blood loss, to name a few. These conditions often lead tolow blood pressure. Furthermore, many medications cause low bloodpressure as a side effect. It is also estimated that as many as 20% ofpeople over the age of 50 have low blood pressure that causeslight-headedness or causes the individual to pass out. Such individualsare at risk especially when they stand up or change position morequickly than their bodies respond to the change in position. Thiscondition is known as orthostatic hypotension. The most commoncardiovascular causes for the loss of consciousness are heartbeatrelated and vessel-related. Pacemakers are commonly used to detect andelectrically stimulate the heart in the event of a long pause or lowheart rate. However, there remains a need to correct low blood pressurecaused by other factors, such as orthostatic hypotension,

The invention described herein may alter blood flow as desired and inresponse to a various number of conditions. For example, and to addressthe concerns described above, a variations of the present inventionaddresses low blood pressure caused by orthostatic hypotension.Accordingly, such conditions may include positional changes in the bodyof the patient, changes in blood flow or pressure within a vessel orvessels, or any other number of conditions.

In both orthostatic hypotension and medication related hypotension thereis insufficient blood pressure to adequately supply blood to the brainwhen the position of the body along with gravity drives blood flow tothe lower part of the body. Under normal conditions, to prevent gravityand certain body positions from draining blood to the lower part of thebody, blood vessels in the lower part of the body quickly become smallerto redirect flow to the brain. However, the effects of aging ormedication impair the body's ability to respond in this manner.Therefore, the effects of these positional body changes become moreprofoundly noticeable with increasing lightheadedness. Syncope occurswith severely reduced blood flow to the brain. Because the physician isunable to do anything for the patient, these patients are frequentlytold to stand up or change positions more slowly in order to counteractthe effects. Obviously, this is only partially effective. It isestimated that more than half of patients presenting for care inemergency departments with syncope have, as a cause, vasodilatation andorthostatic hypotension. However, these patients often require medicalattention for bone fractures, head injuries and other injuries as aresult of their syncope.

BRIEF SUMMARY OF THE INVENTION

One variation of the present invention redirects blood flow preventinglow blood flow to the brain that results in hypotension, syncope and therelated injuries.

A variation of a device in accordance with the invention consists of animplant that alters the flow of blood given a predetermined condition,e.g., given a signal indicating hypotension. As a result, the redirectedblood flow supplies the brain with proportionally more of the total flowpumped by the heart. Therefore, the body reacts over time to thepositional change lessening the effects of syncope. Eventually, thecondition passes, e.g., the body reacts to the change of position, andthe device deactivates allowing the body to function normally.

In another variation of a device suited for syncope, the implantpresents a variable or fixed flow obstruction downstream from vesselsthat supply blood to the brain. The obstruction decreases flow in thesevessels thereby preferentially directing flow to the brain. Thevariability of the obstruction to flow can be adjusted as the bodyreacts to the position change. The implant can be intravascular or extravascular but shall be enabled to receive signals to determine when toconstrict the vessel. It can receive signals from pressure, flow, and/orother detectors that provide for feedback control of the appliance.Alternatively, or in combination, the device may react directly topressure or flow changes within the body in order to directly vary theflow and/or pressure to the brain based on flow and pressure in thevessel where the appliance was implanted. Naturally, the inventioncontemplates safety features to make the device acceptable for humanuse.

It is understood that variations of the details of the design andmethods are possible as are adaptations of the invention describedherein that would not vary substantially from the invention disclosedherein.

It should also be understood that the device can be used in conjunctionwith medications that dilate blood vessels to reduce systemic bloodpressure so that normal blood flow and pressure can be maintained to thebrain while low pressures are provided to the kidneys and other distalorgans. In this way, even patients with refractory hypertension can besuccessfully treated without the most common side effects of orthostatichypotension and syncope that currently limit the success or acceptanceof this therapy.

The present invention modifies the resistance of a vascular system byproviding a variable size member, capable of increasing local vascularresistance and redirecting blood flow from the heart. The presentinvention may redirect flow from within the blood vessel (e.g., a memberthat increases or decreases the effective vessel lumen diameter),external to the blood vessel (by externally compressing the vessel), incombination with drugs, or via a combination of modes as describedherein.

The term variable size is intended to include elastic and inelasticmembers, distensible members (e.g., members that elasticallyexpand/deform), non-distensible members (e.g., members that do notelastically expand/deform but upon expansion assume a predeterminedshape), etc. In one embodiment, the device consists of a variable sizemember surrounding the aorta or other blood vessel. This device may beimplanted percutaneously around a desired vessel location.Alternatively, placement of the device may be performed surgically orminimally invasively. The variable size member is adjusted orself-adjusts when blood pressure reaches a desired level. Additionally,the elasticity of the variable size member may be externally modified tochange the vascular resistance. By precisely modifying the properties ofthe variable size member, blood flow may be redirected as needed.

BRIEF DESCRIPTION THE DRAWINGS

FIG. 1 illustrates a variation of the invention when implanted in thebody.

FIG. 2 illustrates an example of a sensor device for use with theinventive device.

FIG. 3 illustrates a variation of the device for adjustingblood-pressure coupled to an integrating system which may include anelectrical source.

FIG. 4 illustrates an additional variation of the device for adjustingblood-pressure coupled to an integrating system including a pump.

FIG. 5 illustrates the device for adjusting blood-pressure coupled inwhich a chamber is placed between the pump and constriction device.

FIG. 6 illustrates a flow-chart schematic of an example of the feedbackused in the control module to control blood pressure and flow controlwith the device described herein.

DETAILED DESCRIPTION

FIG. 1 shows one variation of the invention. A constricting member,e.g., a variable size member (1), suitable for placement around avessel, for example, around the descending aorta. A sensor (2) monitorsthe condition of the body to activate the constricting member (e.g., thesensor placement is in or around the carotid (17) or other monitoredvessel or the sensor is actually incorporated into the constrictingmember.) The sensor provides information to the integrating module (9)where it is analyzed and used to constrict the constricting member orrelax it. Signals may be sent via wires (15, 16) or through a wirelessinterface. In this way, blood flow is directed to the vessels proximalto the constricting member. This provides relatively increased bloodflow to the vessels supplying the brain, and thereby reduces thesensation of lightheadedness and also reduces syncope with positionalchange.

FIG. 2 shows one example of a sensor configuration (2). It consists of astrain gauge (3), the output of which is directly proportional to thepressure in the vessel proximate to which it has been placed. Thisoutput is sent (e.g., via wires (4)). The sensor can also be constructedto sense flow instead of pressure. Alternatively vessel walldisplacement can be measured and used as a surrogate for flow orpressure.

FIG. 3 shows an example of a constricting member (1). In this example,the member is constructed with a sandwich (5) of elastomeric,electrically-insulating material such as silicone, rubber, latex,hydrogel, or similar material, with two outer surfaces (6) consisting ofelectrically conductive material such as graphite, gold, platinum, orthe like. Wires (7) are connected between the surfaces (6) and thehigh-voltage electrical source (8) through the integrating module (9).When a voltage is applied to the surfaces (6), the attractive forcescompress the elastomeric material (5) causing it to elongate. Elongationrelaxes the constriction.

FIG. 4 shows another variation of a constricting member (1). In thisembodiment the constricting device consists of an inflatable cuff (10)that is inflated by a pump (11) that is controlled by module (9).

FIG. 5 shows a variation where the constricting member (1) is inflatedby a pump (12). In this embodiment, the pump consists of a chamber (13)that is filled with gas or fluid. The pump itself may be constructed ofan insulating material such as Mylar, with a conductive coating such asa metallic ink or paint. The places where the walls of the chamber (13)meet are insulated so as to keep each surface electrically distinct andinsulated from one another. The pump is activated by sending a voltagefrom the high-voltage source (8) as in FIG. 3 to the surfaces of thechamber (13). The charges on the surfaces attract one another and movethe fluid within chamber (13) to the constricting cuff (10) throughconnecting member (14). The cuff may be deflated by pressure within theaorta when the electrical charge is turned off, or actively by chargingboth surfaces of the pump equally, causing the surfaces to repel, andcausing the chamber (13) to increase in size, drawing the fluid or gasback into the chamber (13). The cuff can be variably inflated bymodulating the voltage across the diaphragm. Therefore, the constrictioncan be varied and the pressure modulated by changing the voltage acrossthe chamber (13).

FIG. 6 shows a flow-chart schematic of the feedback used in the controlmodule (9) to accomplish blood pressure and flow control with the pumpand constricting device as shown in FIGS. 4 and 5 or with an integratedconstriction device as shown in FIG. 3.

In addition to the above discussion, the invention includes, but is notlimited to the following: A method of reducing blood flow in a firstportion of the body to increase blood flow in a second portion of thebody in response to a condition as described herein. The method maycomprise contracting a diameter of a vessel in response to a conditionof or within the body.

In the above method the event may comprise generating a signal inresponse to a change to a condition of or within the body. For example,the reduction of blood flow in the first part of the body may comprisereducing flow within a portion of the aorta that is downstream of bloodvessels whose purpose is to provide blood for the brain. The signal maycomprise a decrease in blood flow to the brain, positional changes inthe body of the patient, changes in blood flow or pressure within avessel or vessels, or any other number of conditions.

The devices described herein generally redirect blood-flow as a result achange to a condition within or of the body. In one example, the devicecomprises a variable size member having a passage therethrough, thevariable size member configured for placement within the body; thevariable size member is adapted to reduce a diameter of the passage inresponse to the change to the condition within or of the body.

In these devices and methods, the conditions may be those as describedabove, or other conditions as required by the specific treatment sought.

While embodiments and applications of this invention have been shown anddescribed, it would be apparent to those skilled in the art having thebenefit of this disclosure that many more modifications than mentionedabove are possible without departing from the inventive concepts herein.The invention, therefore, is not to be restricted except in the spiritof the appended claims.

The above illustrations are examples of the invention described herein.Because of the scope of the invention, it is specifically contemplatedthat combinations of aspects of specific embodiments or combinations ofthe specific embodiments themselves are within the scope of thisdisclosure.

1. A device for adjusting blood-pressure in a patient comprising: avariable size member having a body capable of placement around a firstbody vessel portion; the variable size member configured to expand andcontract in response to changes in intra-luminal vessel pressure of atleast a second body vessel portion.
 2. The device according to claim 1,where the variable size member includes an electrically conductivematerial and an elastic material, where the electrically conductivematerial is configured to compress an elastic material to expand andcontract the variable size member.
 3. The device according to claim 2,where the electrically conductive material is located on a surface ofthe elastic material.
 4. The device according to claim 3, where theelectrically conductive material is located on two separate surfaces ofthe variable size member.
 5. The device according to claim 1, furthercomprising a chamber adapted to adjust an elastic compliance of thevariable size member by filling with a medium,.
 6. The device accordingto claim 5, further comprising a reservoir in fluid communication withthe chamber, the reservoir comprising the medium.
 7. The deviceaccording to claim 5 wherein the medium is selected from a groupcomprising a gas and liquid.
 8. The device according to claim 1 whereinthe body comprises an elastic, biocompatible material.
 9. The deviceaccording to claim 8 wherein the body comprises a material selected froma group comprising silicone and urethane.
 10. The device according toclaim 5 wherein the body comprises a resilient material.
 11. The deviceaccording to claim 1 wherein the body comprises an inelastic material.12. The device according to claim 1 wherein the body comprises Mylar andis filled with a second elastic material or gas.
 13. The deviceaccording to claim 2 wherein pressure of the chamber is between 50 and100 mmHg when filled at least partially.
 14. The device according toclaim 2 wherein the device is sized and shaped so as to allow 5 to 100ml of medium to fill the chamber.
 15. The device according to claim 1further, comprising a media port disposed on the body for adding andremoving a medium.
 16. The device according to claim 1 further,comprising an adjustment member to variably secure the variable sizemember about the vessel.
 17. The device according to claim 1, furthercomprising a sensor in electrical communication with the variable sizemember.
 18. The device according to claim 17, where the sensor isconfigured to detect changes in pressure.
 19. The device according toclaim 17, where the sensor is selected from a group consisting of astrain gauge, a flow sensor, and a displacement sensor.
 20. The deviceaccording to claim 1, further comprising a pump in fluid communicationwith the variable size member, where the pump is configured to expandand contract the variable size member.
 21. The device according to claim20, where the pump drives a gas or liquid into the variable size member.22. The device according to claim 20, where the pump comprises anelectrically conductive material, where the conductive materialcompresses upon application of a current.
 23. The device according toclaim 22, where the electrically conductive material comprises Mylar.24. The device according to claim 23, where the electrically conductivematerial comprises a form of a Mylar sac.
 25. The device according toclaim 1, where the variable size member comprise an distensible member.26. The device according to claim 1, where the variable size membercomprise a non-distensible member.
 27. A method for redirecting bloodflow in a first portion of a body lumen to alter blood pressure in asecond portion of a body lumen comprising: connecting a variable sizemember to the first body lumen; the variable size member having aninternal chamber containing a media and altering blood flow in the firstbody lumen using the variable size member.
 28. The method according toclaim 27 wherein connecting the variable size member comprisesconnecting the variable size member externally to the first body lumen.29. The method according to claim 27 wherein connecting the variablesize member comprises connecting the variable size member within thefirst body lumen.
 30. The method according to claim 27 wherein thevariable size member is connected with or without the ability to adjustthe variable size member.
 31. The method according to claim 27 whereinthe media is selected from a group comprising a gas and liquid.
 32. Themethod according to claim 27, where the variable size member comprises aresilient material.
 33. The method according to claim 27, wherein thevariable size member is composed of an elastic, biocompatible material.34. The method according to claim 27, wherein the internal chamber has apressure of between 50 and 100 mmHg when at least partially filled. 35.The method according to claim 27, wherein the variable size memberchamber contains 5 to 100 ml of media.
 36. The method according to claim27, wherein a pressure within the body lumen is adjusted by theadjustment member.
 37. The method according to claim 27, where thevariable size member is placed within the first body lumen.
 38. A methodfor treating orthostatic hypotension comprising reducing blood flow ofat least one blood vessel leading to a portion of the lower body. 39.The method of claim 38, where reducing blood flow comprises externallymechanically compressing the blood vessel.
 40. A device for adjustingblood-pressure in a patient comprising: a blood pressure adjustmentmeans for contracting a lumen in a first blood vessel portion inresponse to changes in intra-luminal vessel pressure of at least asecond blood vessel portion, the blood pressure adjustment means havinga fastener adapted for securing about the first blood vessel portion.41. The device according to claim 40, further comprising a pump meansfor expand and contract the blood pressure adjustment means